What would cause bullets to tumble at 50 yards? I shot a few rounds of Powerbelt 275 and 295 grain with two 50 grain pellets of Triple Seven which was 100 grains total? I could tell they were tumbling at 50 yards according to my target. Ran out of time so never got to shoot over 4-5 times and they were all over the place on the target then. I'm shooting a CVA Accura .50 rifle with 1:28 twist